CBCT Evaluation Of The Upper Airway Space In Skeletal Class Ⅲ Subjects With Different Facial Patterns

Objectives:Numerous studies have established a strong relationship between pharyngeal structures and both dentofacial and craniofacial structures.It was concluded that severe changes in the upper airway may lead to obstructive sleep apnea.Other reports found a strong relation between the vertical growth pattern and pharyngeal airway obstruction.Consequently,the aim of this study is to investigate and compare the 3-dimensional size of the pharyngeal airway space among skeletal class Ⅲ adult subjects with different vertical growth patterns(low,normal,and high angle)and skeletal class Ⅰ adult control subjects,consisting of Chinese adults.The secondary aim is to ascertain whether sexual dimorphism correlates with pharyngeal airway space size.Material and Methods:Pretreatment Cone Beam Computed Tomography(CBCT)scans of80 adult patients,between 18-30 years old(mean age 23.68±4.025 years),were selected among the patients who visited in the department of orthodontics at the Second affiliated hospital of Dalian Medical University from 2018-2020.The sample is composed of 60skeletal class Ⅲ patients(33 males and 27 females)and 20 skeletal class Ⅰ patients as a control group.Skeletal class Ⅲ sample groups were grouped by vertical facial pattern and anteroposterior jaw relationship.They were classified according to both their vertical pattern(High N=20,Normal N=20 and Low angle N=20)and anteroposterior jaw relationship(Maxillary deficiency N=27,Mandibular prognathism N=33).CBCT scans were used to evaluate the pharyngeal airway volume and minimum constriction area.This was done by using 3-dimensional virtual surface models to calculate airway volumes,instead of estimates based on linear measurements.Analysis of variance(ANOVA)with a two-criteria fixed model and the post hoc Tukey test considering a significance level of<0.05 were used to identify the differences within and among groups.Results:In the vertical group,the volume and the minimum constriction area was greatest in the low angle subgroup(25.1 mm~3and 274.4 mm~2respectively)and had a statistical significant difference when compared to the other subgroups(high angle,normal angle and skeletal class Ⅰ control group)of the same group.The high angle subgroup had the lowest means of volume and minimum constriction area(19.5 mm~3 and 194 mm~2 respectively)among class Ⅲ vertical subgroups.In the anteroposterior group,the mean volume of the pharyngeal airway space and minimum constriction were statistically greater in skeletal class Ⅲ patients when compared to class Ⅰ control group.The mandibular prognathism subgroup(VOL 23.05 mm~3)showed a statistically significant difference when comparing the volume of the pharyngeal airway space to the maxillary deficiency and skeletal class Ⅰ control group.The males in Skeletal class Ⅲ had a statistically significant increase in the pharyngeal airway volume(VOL 22.7 mm~3)when compared to the female group(VOL 20.4 mm~3,p value=0.043).The minimum constriction was larger in the males group,but this result did not show a statistical difference.Conclusion:The findings generated from the present study support the hypothesis that the pharyngeal airway volume is smaller in high angle patients in Skeletal class Ⅲ in comparison to normal and low angle patients of the same skeletal malocclusion.This confirms an association between pharyngeal airway space and the vertical skeletal pattern.Furthermore,females of skeletal class Ⅲ had a reduced airway volume compared to that of males.These findings have clinical implications that should be taken into account during both diagnosis and treatment planning.